The purpose of these investigations is to determine the hemodynamic changes that occur in normal and partially obstructed coronary arteries in the same fasting dogs at rest and with exercise, and during digestion at rest and during exercise. An interrelationship between splanchnic and coronary blood flow has been suggested as the cause of post prandial angina. The dogs described above, will also have flow probes and pneumatic occluders placed on the superior mesenteric artery, which will permit studies of splanchnic vascular insufficiency and its effects on coronary blood flow. Obstructive lesions of known severity in the coronary arteries will be produced and evaluated by coronary arteriography, and by a casting technique at necropsy. After weeks to months of chronic partial coronary artery obstruction, a saphenous vein bypass graft with a flowmeter probe attached will be implanted distal to the area of obstruction. We will determine if the normal control mechanisms which may be lost during chronic ischemia, return to the arterioles when blood flow is restored.